Apparatus to assist a patient&#39;s breathing with a variable ramp period to rise to treatment pressure

ABSTRACT

An apparatus ( 1 ) to assist a patient&#39;s respiration by delivering air to a patient through a mask ( 20 ), including a ramp module ( 10 ) connected to a control unit ( 2 ) to provide the control unit with a pressure value P M  at mask ( 20 ), so that when apparatus ( 1 ) starts functioning, the pressure progressively rises until it reaches a treatment pressure PTi, the apparatus further including a comparator connected to ramp module ( 10 ), at least one device for detecting the patient&#39;s breathing parameters and sending them to the comparator, so that the comparator can determine whether an event (E 1 , E 2  or E 3 ) occurs in patient&#39;s breathing and to send the corresponding data to ramp module ( 10 ) which provides control unit ( 2 ) with a pressure value P M  that will speed up with respect of time, so that the pressure rise at patient&#39;s mask ( 20 ) is accelerated.

TECHNICAL FIELD

This invention concerns the field of apparatus to assist a patientrespiration and more specifically an apparatus bringing progressively tothe pressure of treatment the air the patient is provided with.

BACKGROUND ART

In many treatments apparatus are used to provide patients with air. Morefrequently they are used for patients with a breathing deficiency causedfor example by the weakness of the breathing system or by obstructiveapneas during the sleep. In those cases it is important to control thepressure of the air delivered to the patient. With respiratoryinsufficient patients, apparatus providing air at a higher pressure helpto compensate the weakness of the patients lungs. In the case ofpatients suffering of sleep apneas, providing the air at a higherpressure removes the obstruction of the upper airways.

The pressure of treatment is usually not strong enough to wake thepatient up, but can prevent him from falling asleep. An implementationof treatments apparatus is to wait for the patient to fall asleep beforeproviding air under the treatment pressure. The classical solution is tohave a ramp period, which is a slow increase of the delivered pressurefrom a low level to the treatment pressure.

Still to enhance the comfort of the patient, it is disclosed in patentU.S. Pat. No. 5,492,113 and U.S. Pat. No. 5,970,975 an apparatus whereinseveral cycles of ramp are provided on patient's conscious demand. Thecycles actuated after the first cycle rise faster in pressure. All thoseramps are predetermined in shape and duration. The patient can alsoselect a fastest shape of ramp or select one special shape in order tofall asleep more easily. This selection being made among differentpredetermined shapes of ramp. However, such devices require from thepatient a minimum of consciousness to activate the ramp cycles. This isnot really very efficient to fall asleep and it is not possible when thepatient as fallen asleep.

Moreover each ramp can not be modified during the time when the ramp isactivated.

SUMMARY OF THE INVENTION

The first object of the invention is to provide a ramp that would beable to modulate automatically, especially when the patient fallsasleep.

A second object of the invention is to provide in any case a maximum oftime in rise of pressure, in order to apply the treatment in any case.

The invention thus concerns an apparatus to assist a patient respirationby delivering air to a patient trough a mask, comprising:

-   -   a blower to provide the patient with air under a treatment        pressure,    -   a control unit to adjust the pressure delivered by the blower at        the level of the patient's mask,    -   a ramp module connected to the control unit in order to provide        the control unit with the value of pressure P_(M) to settle at        the mask, so that when the apparatus starts functioning, the        pressure progressively rises until the pressure of treatment        P_(T);    -   the apparatus comprising a comparator connected to the ramp        module, means for detecting the patient's breathing parameters        and sending them to said comparator, in order that in response        to breathing parameters, the comparator is able to determine        that an event occurs in patient's breathing and to send the        corresponding data to the ramp module which provides the control        unit with a value of pressure P_(M) that will speed up with        respect of the time, so that the rise of pressure at patient's        mask is accelerated.

In an implementation of the invention, the value of pressure P_(M) hasalways maximum and/or minimum limits so that the increase of pressure isalso limited in minimum and/or maximum.

Such an apparatus has the advantage to generate a ramp period which canbe modulated in the same ramp, according to patient's breathingparameters.

BRIEF DESCRIPTION OF FIGURES

The purposes, objects and characteristics of the invention will becomemore apparent from the following description when taken in conjunctionwith the accompanying drawings in which:

FIG. 1 represents the apparatus schema,

FIG. 2 represents the pressure delivered to the patient's mask accordingto special events occurring in patient's breathing,

FIG. 3 represents the domain of pressure increase, and

FIG. 4 represents the block diagram for the ramp period.

DETAILED DESCRIPTION OF THE INVENTION

The apparatus according to the present invention is able to generate aramp period which can be modulated in respect of the time required bythe patient for falling asleep.

The apparatus as represented in FIG. 1 comprises a blower 4 to providethe patient with air. This blower is connected to a tube 8 on a firstextremity, the second extremity being connected to the mask 20 whereinthe patient breathes. A control unit 2 provides the blower 10 with theelectrical control required to enable the blower to function in order toset a given pressure at the patient's mask or blower's outlet. Thispressure could be by a pressure transducer 6 at the mask level or at thetube extremity, which is connected to the mask. A ramp module 10 isconnected to the control unit 2 and to the pressure transducer 6. Theramp module provides the control unit 2 with the pressure at thepatient's mask and with the pressure to settle at the patient's mask atthe starting of the apparatus 1 functioning. During the treatment thecontrol unit 2 is able to detect breathing events according to thepressure sensor 6 or any other way to evaluate or measure the patient'sairflow. Such detection can be given by airflow sensors which providethe control unit with pressure parameters, the control units being thusable to detect that an event is occurring.

The apparatus according to the present invention is able to modulate therise in pressure during one single ramp period, which is impossible toperform for apparatus of prior art. The apparatus comprises a rampmodule 10 connected to the control unit 2 in order to provide thecontrol unit with the value of pressure P_(M) to settle at the patient'smask, so that when said apparatus starts functioning, the pressureprogressively rises until the pressure of treatment P_(T). The apparatuscomprises a comparator which is not represented in FIG. 1 and that canbe comprised in the control unit 2. This comparator is connected to theramp module 10. The apparatus comprise also at least one means fordetecting the patients breathing parameters and sending them to saidcomparator, in order that in response to said breathing parameters, thecomparator is able according to determine that an event occurs inpatient breathing and to send the corresponding data to the ramp modulewhich provide the control unit 2 with a value of pressure P_(M) thatwill speed up in respect of the time, so that the rise of pressure atpatient's mask is accelerated.

According to a preferred embodiment, the ramp module 10 provides thevalue of pressure P_(M) being a linear function of time wherein theincrease coefficient K_(RP) is constant, said ramp module increasingthat coefficient of a constant value K_(E) when the control unit 2 senda data corresponding to the event which occurred.

In the apparatus 1 according to the present invention, a minimum speedof rise in pressure until the treatment pressure is set, as representedby the curve C₂ on FIG. 3. This minimum rise of pressure in respect oftime is called in the present application a safety ramp C₂. Before theramps period starts at the instant t_(S), a minimum starting pressure P₀is delivered. After the instant t_(S), even if the patient is notasleep, the pressure at the mask will start rising. In any case at theinstant t_(T), the treatment pressure will be reached; this means thatthe curve C2 represents the minimum speed of rise in pressure. In apreferential implementation of the invention, the minimum speed of risein pressure is proportional to time, the coefficient to rise in pressureaccording to time being K_(SR). Also it can be set a maximum of rise inpressure as represented by the curve C₁ on FIG. 3. The maximum of risein pressure can also be given a linear function of time. Between thesetwo limits the rising of the pressure can be modulated by the controlunit 2 in respect of the patient's falling asleep. That is to say thatwhenever any events occurs or not, the pressure provided at thepatient's mask P_(PM) before the time of plain treatment t_(T) will becomprised between these two limits, this domain of pressure variationsbeing represented in FIG. 3 by the hachures.

When a patient is asleep his respiration becomes stable, this is used todetect the instant when the patient falls asleep. Another way to detectwhen the patient falls asleep is to detect the drop of frequency betweenthe awake rate breathing and the awake breathing. As represented in FIG.4 and according to a preferential implementation, the control unit 2transmits the ramp module an output average pressure value P_(M) whichis the pressure value required to patient's mask. When the patient isabout to fall asleep, his respiration becomes stable. In that case theP_(M) value is increased, preferentially as a linear function of time,the proportional coefficient being K_(RP). If the pressure value P_(M)is inferior to the safety ramp pressure P_(SR), the pressure P_(M) isset to the value of the safety ramp pressure P_(SR), which is in apreferential implementation calculated by the module ramp 10 bymultiplying the time spent from the beginning of the ramp routine to thepresent time by the coefficient K_(SP). When the pressure value P_(M)equals or is superior to the treatment pressure P_(T), the P_(M)pressure is maintained equal to the treatment pressure value P_(T). Onthe contrary the control unit 2 checks again if the respiration isstable. This shows that until the patient falls asleep the P_(M) valuewill not be superior to the treatment pressure P_(T), and will onlyequals it when the patient falls asleep or when the safety ramp reachesthe treatment pressure value. This also shows that during the rampperiod, if the respiration is stable, the air provided can rise fasterthan the safety ramp. In that case, the coefficient K_(RP) will behigher than the coefficient K_(SP). The ramp module will thus enable tothe control unit to accelerate the rise in pressure when the patientsfall asleep and when no events are detected.

An other implementation of the apparatus according to the presentinvention is that when the control unit detects an event in patientsbreathing that shows an asleep state, the control unit will provide theramp module 10 with the information. The ramp module will thus increaseagain the rise in pressure.

The following are examples of ramp periods generated by the apparatusaccording the present invention.

EXAMPLE 1 Variations of Value P_(M) According to Different Events

FIG. 2 represents one example of the apparatus functioning wherein threesystems of coordinates are represented: pressure value PM as a functionof time, patient's breathing B as a function of time and snoring S as afunction of time. At a time t_(S), the ramp module 10 activates the risein pressure. At time t₁ as a slowdown E₁ in breathing is detected, therise in pressure is accelerated by the ramp module 10. Then at time t₂snoring E₂ is detected. Thus, the rise in pressure is accelerated againby the ramp module. As at time t₃ a snoring E₃ is still detected theramp module still accelerates the rise in pressure. As represented onFIG. 2, the preferred embodiment is a linear rise in pressure. Thus attime t_(S), the coefficient K_(RP) of rise in pressure is constant. Eachtime an event is detected the module ramp adds a given constant valueK_(E) to this coefficient, the slope of the linear function being thusaccentuated at each event. This will last until the treatment pressureP_(T) is raised. Then the ramp is completed and the control unit appliesthe treatment pressure to the patient's mask. The value K_(E) can be setby the physician in a non volatile memory and can be different accordingto the event detected.

EXAMPLE 2 Example of Calculating the Value P_(M)

In this example the treatment pressure P_(T) is of 10 hecto pascal(hPa). The initial pressure P₀ of the air provided at patient's mask is4 hPa. A physician has set that the ramp will start at a time ts of 2minutes and has set the initial coefficient K_(RP) at 0.2 hPa per minute(hPa/mn). The physician also set that when a snoring is detected K_(E)equals 1 hPa when the breath rate is below a set threshold.

When the apparatus starts the control units supply the blower in orderto set at the patient's mask a pressure of 4 hPa. After 2 minutes, theramp module starts increasing the value P_(M). As no events occurs, thecoefficient K_(RP) stays at 0.2 hPa. After 10 minutes the value P_(M) isof 5.6 hPa (8 minutes multiplied by 0.2 hPa/mn and added to the 4 hPa).After these ten minutes, the patient's breath is below threshold. Theramp module adds the corresponding K_(E) value to the coefficientK_(RP), which thus equals 1.2 hPa/mn. The treatment pressure is thusraised in about 13 minutes and 40 seconds.

1-8. (canceled)
 9. An apparatus to assist a patient's respiration bydelivering air to a patient through a mask, comprising: a blower toprovide the patient with air under a treatment pressure, a control unitto adjust the pressure delivered by said blower at the level of saidmask, a ramp module connected to the control unit in order to providethe control unit with a value of pressure P_(M) to settle at said mask,so that when said apparatus starts functioning, the pressureprogressively rises until the pressure of treatment P_(T); and acomparator connected to the ramp module, at least one means fordetecting the patient's breathing parameters and sending them to saidcomparator such that the comparator is able to determine whether anevent (E₁, E₂ or E₃) occurs in patient's breathing based on saidbreathing parameters and to send the corresponding data to the rampmodule which provides the control unit with a value of pressure P_(M)that will speed up with respect of time, so that the rise of pressure atpatient's mask is accelerated within the time when the ramp isactivated.
 10. The apparatus according to claim 9, wherein said rampmodule provides the value of pressure P_(m) being a linear function oftime wherein an increase coefficient K_(RP) is constant, said rampmodule increasing that coefficient of a constant value K_(E) when thecontrol unit sends a data corresponding to said event (E₁, E₂ or E₃).11. The apparatus according to claim 9, wherein the value of pressureP_(M) has always maximum and/or minimum limits so that the increase ofpressure is also limited in minimum and/or maximum.
 12. The apparatusaccording to claim 10, wherein said ramp module comprises a memory wherea minimum coefficient K_(SRP) is stored, said ramp module alwaysmaintaining the coefficient K_(SRP) equal or greater than said minimumcoefficient K_(SRP), so that the ramp module provides the control unitwith a value of pressure P_(M) always greater than a minimum limit. 13.The apparatus according to claim 10, wherein said ramp module comprisesa memory where a maximum coefficient K_(MRP) is stored, said ramp modulealways maintaining the coefficient K_(RP) equal or less than saidmaximum coefficient K_(MRP), so that the ramp module provides thecontrol unit with a value of pressure P_(M) always less than a maximumlimit.
 14. The apparatus according to claim 9, wherein said means fordetecting the patient's breathing parameters enable the control unit tocompute the airflow at patient's mask, said comparator determiningwhether an event (E₁, E₂ or E₃) is occurring with the airflow parametersor shape.
 15. The apparatus according to claim 9, wherein the rampmodule increases the value of pressure P_(M) when an anomaly inpatient's breathing is detected.
 16. The apparatus of claim 15, whereinsaid anomaly is either snoring or apnea.
 17. The apparatus according toclaim 9, wherein the ramp module increases the value of pressure P_(M)when the patient's breathing parameters correspond to a drop betweenawake breathing and asleep breathing or when they correspond to a stablefrequency of breathing.